This application is based on Application No. 2000-166141, filed in Japan on Jun. 2, 2000, the contents of which are hereby incorporated by reference.
This invention relates to a gas-insulated switchgear and, more particularly, to a gas-insulated switchgear having a device for interrupting an electric power system upon the generation of a failure in the power system and having a dual bus bar structure.
FIG. 4 illustrates a conventional gas-insulated switchgear having a dual bus conductor structure disclosed in Japanese Utility Model Laid-Open No. 2-23049. In the figure, the reference numeral 1 depicts circuit interrupters, 2 are bus conductor side and line side disconnectors, the one disposed at the lower position is a line side disconnector to be connected to a line through a cable head which will be described later. 3 is a grounding switchgear, 4 is a potential current transformer, 5 are cable heads, 6 are main bus conductors, 7 are connection conductors, 8 is an electrically insulating gas, 9 is a cubicle outer shell vessel containing therein together components of this apparatus, such as the disconnectors 2, the grounding switchgear 3, the potential current transformer 4, the cable heads 5, the main bus conductors 6 and the connection conductors 7. 10 are separate metal vessel containing therein the main bus conductors 6 and the bus conductor side disconnectors 2, the metal vessels 10 being hollow cylinders having a circular or substantially elongated circular cross section and filled with an electrically insulating gas at 5 kgf/cm2 (gauge pressure).
As understood from FIG. 4, the maintenance and the inspection of the components disposed within the cubicle outer shell vessel 9 of the conventional gas-insulated switchgear can be achieved without the need for interrupting the power supply to the main bus conductors 6. However, since the switchgear has a junction structure for making the bus conductor side disconnectors 2 and the connection conductors 7 separable in case of the need for separating the cubicle outer shell vessel 9 from the metal vessel 10, the number of parts is large and structure is complicated. Also, the points of separation of the dual bus conductors are located inside of the outer shell vessel 9, so that the realization of a large current-carrying capacity is significantly affected and impeded by the temperature rise within the outer shell vessel 9.
Accordingly, a main object of the present invention is to provide a gas-insulated switchgear that has a simple structure and a small number of parts and that is small in temperature rise within the outer shell vessel so that the current-carrying capacity is significantly increased.
With the above object in view, the present invention resides in a gas-insulated switchgear comprising a first hermetic vessel filled with an electrically insulating gas and having accommodated therein a circuit interrupter for interrupting a circuit and a disconnector disconnecting the circuit. A second hermetic vessel filled with an electrically insulating gas and having accommodated therein a disconnector and a third hermetic vessel disposed in parallel to said second hermetic vessel and filled with an electrically insulating gas and having accommodated therein a disconnector for disconnecting the circuit. The switchgear also comprises shunt conductors connected in parallel to each other between said disconnector within said first hermetic vessel and said disconnectors within said first and second hermetic vessels. The shunt conductors each comprises a conductor having terminal portions extending through and penetrating into said first hermetic vessel and said second and third hermetic vessels and a main body portion connected and shunted between said terminal portions for parallel distributing an electric power from said first hermetic vessel to said second and third hermetic vessels, an insulating material covering said main body portion, and an electrically conductive coating disposed on an outer surface of said insulating material and grounded.
The main body portion of the conductor may be disposed outside of the hermetic vessel.
Each of the terminal portions of the conductor may comprise a conductor for pivotally supporting a movable contact blade of the disconnector within the hermetic vessel.
At least three of the shunt conductors may be provided.